Technical Field
The technical field of this disclosure relates generally to medical devices, and more particularly to methods and apparatus for assessing blood flow in patients.
Background Discussion
Assessment of the status of the vascular access region (e.g., a vein) in hemodialysis patients is routinely one of the most important challenges in clinical practice. Hemodialysis patients depend on the vascular access to connect to a hemodialysis machine that provides life-saving filtration of waste products from the blood stream of the patient. The vascular access of a patient, however, may fail because of blood clotting in and/or around the vascular access. Eventually, the patients who experience vascular access failure may have to undergo surgery to improve blood flow in the vascular access.
A current standard practice to access the health of the vascular access is to use Doppler ultrasound techniques to generate ultrasound images of the vascular access. In clinical practice, a physician reviews the ultrasound images of the vascular access to assess the health of the vascular access based on the physician's experience. However, there is no standard practice to obtain the ultrasound images. Accordingly, the quality of the resulting ultrasound images may be inconsistent based on, for example, the way the ultrasound probe is held against the patient and which areas of the patient are imaged. Ultrasound imaging also requires a skilled operator, is location-dependent, and is time-consuming.
Electromagnetic flowmeters have also been used, in an industrial setting, in assessing blood flow. Yet attempts to apply such techniques in a clinical practice have had limited success due to a lack of accuracy, and insensitive specific location of blood flow.